The purpose of this study is to examine the adverse effects of illicit drug use on the legs, namely, early-onset chronic venous insufficiency (CVI), loss of mobility, and leg pain. Ranging from minor skin changes to leg ulcers that are difficult to heal, CVI is associated with restricted functioning, pain and suffering. Even persons who have stopped injecting drugs remain at risk. Our preliminary research indicates that this is a major health problem among those who have used injection drugs occurring with a prevalence of 87% in a large methadone clinic sample. The central hypotheses are that (a) the high prevalence of early onset CVI is a consequence of venous damage in the lower extremities due to injection drugs and (b) leg pain and the ensuing reduction in mobility further exacerbate the disease. Two specific aims will be addressed: (a) establish that injection use is responsible for early onset CVI and determine what other drug use variables moderate this effect, and (b) determine how ankle and general mobility and leg pain are associated with early onset CVI. This is an observation/comparative design. Clients (N=600), 30 to 60 years of age, will be recruited from substance abuse treatment centers. Eligible participants will be stratified into 3 groups according to route/site of illicit drug use. Selective sampling and statistical controls will be used to increase comparability of groups. Objective and self-report measures of drug use, leg pain, mobility, and CVI will be obtained individually form each participant. Descriptive, inferential, and structural equation model building will be used. We will extend our prior research to show the conditions under which injection drug use is responsible for early-onset CVI. We will examine leg pain and mobility as potential modifiable links between injection drug use and CVI. This research is significant because it will aid in our understanding of the mechanism of CVI and support the development of evidenced-based programs to promote leg health for those who have used injected drugs. [unreadable] [unreadable]